The specific aims of this study are the following: 1. To improve the dose efficiency in pediatric radiography by a factor of 5-10 through a systematic approach to optimal utilization of current state-of-the-art film/screen technology (i.e., rare-earth screens, microfocus tubes, carbon fiber material and selective beam filtration); 2. To test the dose efficiency model as developed by the investigators for the assessment of the information/dose ratio, in the development of optimal pediatric radiography system(s); 3. To assemble the most dose efficient stationary and portable radiography system(s) based on the results obtained; 4. To evaluate clinical results with the above system(s) in pediatric chest and abdomen examinations; 5. To provide a model for a systematic approach to optimizing standard screen/film radiography systems which may result in a 5-10x dose reduction with comparable image quality, at little added cost. The technique of contrast-detail-dose analysis as described by the investigators is used in this study. The thresholds perceptibility of disks of varying contrast and sizes is examined as a function of exposure, x-ray energy, scatter, film/screen combination, and system geometry and the results plotted on contrast-detail-dose visibility diagrams. The dose efficiency is derived from these diagrams by comparing the results to those theoretically obtainable by an ideal system.